The present invention relates to a connector unit for electrical and removable connection of primary and secondary electric devices and, in particular, to the connector unit which comprises primary and secondary connectors connected to the primary and the secondary electric devices.
In a conventional connector unit of the type described above, the primary and the secondary connectors generally comprise a plurality of primary and secondary contact leads, respectively. Furthermore, at least one of the primary and the secondary connectors (for example, the primary connector) is generally a right-angle type so that one (primary) contact lead is arranged over top of another in turn. Namely, one primary contact lead is arranged over top of another in a height direction of the primary connector.
When the primary and the secondary connectors are connected to each other, the primary contact leads and the secondary contact leads are connected to each other, respectively, to thereby form a plurality of signal paths for transmitting signals, respectively. The signal paths have different lengths from one another. This is because one primary contact lead is longer than another as mentioned above. Therefore, signals transmitted through the signal paths are different from one another in delay or passage time. The delay-time difference among transmission of signal is often called "skew".
Recently, the connector unit is requested to transmit high frequency signal at a high speed when applied to such electric devices as a circuit board provided with a large scale integrated semiconductor chip, a data storage device, and so on. However, the electric devices can not perform their functions at a desired high speed by signal transmission through the conventional connector unit because the signals transmitted through the signal paths have different delay times as described above.
Furthermore, the connector unit is also required to increase a number of signal paths because the electric devices recently tend to because large in the number of input/output signals. In the conventional connector unit, when the number of signal paths is increased, the numbers of the primary contact leads and the secondary contact leads must be also increased. This results in an increase of a difference between the shortest length and the longest one of the primary contact leads. As the difference in length among the signal paths becomes large, a difference among the time delays are also increased.
Also, the connector unit is required to reduce a size thereof because electric devices having a compact size suitable for a mobile and/or a small place use are recently required. Particularly, the connector unit is required to reduce a height thereof when mounted on the electric device such as the circuit board. When heights of the connectors are reduced while the number of signal paths is increased as mentioned above, the primary and the secondary contact leads arranged in the connectors must be arranged at a very short pitch. Such a very short pitch of arrangement increases a cross talk between adjacent ones of the contacts.
In order to transmit a high frequency signal, two conventional connectors are disclosed for example in Japanese Patent Unexamined Publications (JF-A) Nos. 315916/1996 and 122335/1995, respectively. The connectors have the contact leads arranged at a slant in order to shorten lengths thereof. Furthermore, the signal content leads are arranged alternately with the ground contact leads and/or the signal contact leads are surrounded by the ground contact leads. Thus, this structure enables improvement of the cross talk mentioned above. However, the skew is not much improved by both the connectors maintained in both of the publications. In addition, the height and/or the size can not be small with both the connectors.